Well, since I also use all of those men in my regular guard army, they would have a pretty standard assortment of heavy weapons. In a true conscript army, though I would want to max out flamers and heavy bolters. It's important to max out your number of shots for maximum effect. Flamers are great because they don't need BS, and with three heavy bolter shots you usually get at least one hit. I personally would leave anti-armor to the tanks and the support squads on the command platoon, but if you wanted to give your conscripts anti-tank firepower, I would recommend autocannon over missile launchers. You double your chances of getting a hit, while a missile only increases your chances of doing damage by 1/6th.